IEEE802.16 WG (Working Group) defines Point-to-Multipoint (P-MP) type communication system in which a plurality of terminals can be connected to a wireless base station. Mainly, IEEE802.16 WG defines two types, that is, IEEE802.16d specification (802.16-2004) mainly for fixed communication application and 802.16e specification (802.16e-2005) for mobile communication application. Where, plural physical layers are defined and techniques such as OFDM, OFDMA and the like are mainly used.
In a communication system in conformity with IEEE802.16d/e (hereinafter, generally named as IEEE802.16), P-MP type connection where a plurality of wireless mobile stations (MSs) are connected to one wireless base station (BS) is possible. Incidentally, wireless mobile station includes various terminals such as cellular phone, PDA, note PC, etc.
According to IEEE802.16, the BS allocates a wireless bandwidth to an MS when the MS transmits data. When the MS makes a request for allocation of a bandwidth used for data transmission to the BS, the MS should first transmit a code in a predetermined pattern called “Bandwidth Request CDMA Code” (hereinafter, referred as BR code).
BR code is a kind of CDMA codes, and part of CDMA codes, which are defined up to 256 in number, is used as BR code. Other CDMA codes are used for Initial Ranging performed when the MS starts a connection with the BS, Periodic Ranging after the connection is established, etc. Incidentally, these CDMA codes are generally called ranging codes, occasionally.
FIG. 21 illustrates a sequence from when the MS transmits a BR code to when a bandwidth for data transmission is actually allocated.
When the MS makes a request for a bandwidth of wireless resource (uplink:UL) to transmit data to the BS, the MS chooses at random one of CDMA codes defined as the BR codes, and transmits the chosen CDMA code to the BS (step S101).
The BS having received the BR code transmits an uplink map message (UL-MAP message) containing an information element called “CDMA_Allocation-IE” in order to allocate a wireless resource [band(width)] that the MS uses to transmit a message called “Bandwidth Request Header” (hereinafter, referred as BR header) (step S102).
In table 1, an example of payload of UL-MAP message containing CDMA_Allocation-IE.
TABLE 1UL-MAP message containing CDMA_Allocation-IEFieldField NameLengthValueUL-MAP messageManagement Message Type8b3 (representing UL-MAPmessage)Reserved8bUCD count8bAllocation Start Time32b No. OFDMA Symbols8bNumber of Symbols for ULsubframe<UL-MAP_IE for OFDMA PHY>UIUC4b14 (representingCDMA_Allocation-IE)<CDMA_Allocation-IE>32b Duration6bNumber of Slots(representing anallocation amount ofwireless resource)UIUC4bRepresenting modulationscheme and codingscheme/rate to be usedRepetition Coding2bRepresenting repetitionInformationcodeRanging Code8bRepresenting CDMA CodeIndex received by BSRanging Symbol8bRepresenting at whichsymbol a code received byBS is placedRanging Subchannel7bRepresenting in whichsubchannel a codereceived by BS is placedBandwidth Request1bRepresenting whether MSMandatorytransmits BR Header ingiven wireless resource
The MS having received the BR code can discriminate whether a wireless resource is allocated to its own station or not from Ranging Code, Ranging Symbol and Ranging Subchannel contained in CDMA_Allocation-IE.
The MS receives the UL-MAP message, and transmits a BR header in an allocated bandwidth to the BS when the bandwidth to transmit a BR header is allocated (step S103). The BR header contains identification information (CID) on a logical connection between the MS and the BS, setting of which is requested by the MS, and information on a size (the number of bytes) of data that the MS desires to transmit.
FIG. 22 illustrates an example of BR header format. Table 2 below illustrates meaning of each field of the BR header.
TABLE 2Bandwidth Request Header FieldField NameDescriptionHT: Header Type1 = Bandwidth request headerEC: Encryption Control0 = Payload is not encryptedTypeBandwidth Request Type000: incremental001: aggregateBR: Bandwidth RequestThe number of bytes of uplinkbandwidth requested by theSS. The request shall notinclude any PHY overhead.CID: Connection IdentifierRequesting Connection ID.HCS: Header Check SequenceUsed to detect header errors
From CID contained in this BR header, the BS can specify an MS that has transmitted the BR header (this MS having completed network entry and association between the MS and CID being managed on the network's side), and can specify a connection for which the wireless resource (bandwidth) is requested and service quality (QoS: Quality of Service) information thereon. Incidentally, QoS information is exchanged between the BS and the MS at the time of connection setting.
The BS determines whether to allocate the requested bandwidth for data transmission, in consideration of the QoS information. In other words, when receiving requests (BR headers) from plural MSs, the BS gives preference to a connection where high QoS is requested, and allocates a bandwidth. Allocation of bandwidth is performed by transmitting an UL-MAP message by the BS (step S104).
Since the BS having received the BR header or the like can specify a CID to which allocation of wireless resource is necessary, the BS can allocate the wireless resource with the use of a message (UL-MAP message) in a format differing from one used at the time of allocation in response to reception of the BR code.
Table 3 below illustrates an example of UL-MAP message generated by the BS in response to reception of BR header or the like.
TABLE 3UL-MAP message responsive to BR headerFieldField NameLengthValueUL-MAP messageManagement Message8b3 (representingTypeUL-MAPmessage)Reserved8bUCD count8bAllocation Start Time32b No. OFDMA Symbols8bNumber ofSymbols for ULsubframe<UL-MAP_IE for OFDMA PHY>CID16b RepresentingMS to beallocatedwirelessresourceUIUC4bRepresentingmodulationscheme andcodingscheme/rate tobe usedDuration10b Number of Slots(representingan allocationamount ofwirelessresource)Repetition2bRepresentingCodingrepetitionInformationcode
The MS transmits data (MAC-PDU: Medium Access Control—Protocol Data Unit) with the use of a bandwidth allocated in the UL-MAP message (step S105).
In Patent Document 1 below, specific code and data amount to be transmitted from the MS to the BS are associated with each other.    Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2007-184936    Non-Patent Document 1: IEEE Std 802.16™ 2004    Non-Patent Document 2: IEEE Std 802.16e™ 2005